danwat1234
Posts: 41
Joined: Sun Nov 14, 2010 9:19 pm

How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 2:47 pm

Does anybody know what is the primary circuitry that recharges the 12V lead acid battery? How many amps can it recharge at? hopefully something above 40 amps @ 13.5V.

I am thinking about powering a device off the 12V battery 24/7 and if the car will automatically detect that the charge is getting a bit low and charge up the 12V even if the car is "off". My guess would be that it would not charge up the 12V when the car is off, the circuitry detecting the voltage would probably be off, but who knows.


Thanks.

mitch672
Posts: 1956
Joined: Fri Apr 23, 2010 2:10 pm
Location: Boston, MA

Re: How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 2:57 pm

I can only tell you how it's done on a Prius, and thats with a DC-DC inverter, that can supply up to about 100A @ 12VDC

I'm sure it's very similar on the Leaf, and no, it doesn't work when the car is off (at least on a Prius)
2012 Advanced Plug in Prius (sold)
I Support OpenEVSE: http://code.google.com/p/open-evse/" onclick="window.open(this.href);return false;
My Fuelly page: http://www.fuelly.com/driver/mitch672/prius-plugin" onclick="window.open(this.href);return false;
Tesla Model S 85KW Dolphin Grey VIN: 03245, delivered 1/17/2013

User avatar
mwalsh
Posts: 9644
Joined: Thu Apr 22, 2010 10:10 am
Delivery Date: 05 Jan 2011
Leaf Number: 0213
Location: Garden Grove, CA

Re: How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 4:05 pm

What about the solar panel on the SL's spoiler? That should keep working as long as it's getting light, right?
2011 Blue Ocean SL with 83,000 miles
2015 pack on 12/30/15
Tinted windows
Bosch AGM 12v
Ecopia 422+ tires
L1 EVSE upgrade
FIAMM horns
Superbright LED lighting
2013 sun visors
LED shifter
Heated seats
GT-R map lamp lenses
Altima illuminated door switches

User avatar
EVDRIVER
Moderator
Posts: 6677
Joined: Sat Apr 24, 2010 7:51 am

Re: How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 4:28 pm

This has been discussed multiple times on many threads. The DC/DC charges the battery, not sure the charge current but it will be high likely. The DC/DC is off when key is off. What does the charge rate have to do with having something on? What type of constant load are you looking to have on all the time. if you give me details I can give you better info. The solar panel generates very little power and just trickle charges the 12V battery.

User avatar
LTLFTcomposite
Posts: 4696
Joined: Fri Apr 23, 2010 6:06 pm
Delivery Date: 10 Dec 2011
Leaf Number: 5926
Location: Central FL

Re: How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 4:50 pm

Something I've been wondering about the 12v battery though I haven't seen discussed... as an armchair EV engineer I'll submit this for your consideration...

"Hard driving" (acceleration, hill climbing, maybe lots of regen braking) shortens the life of the battery pack, right? i.e. the pack will last longer if you baby it, keeping the charging and discharging rates low? So how about "front ending" the big, expensive battery pack with a (much smaller) cheap lead acid battery that can absorb the "surges" and smooth out the current spikes to the main pack? So what if you have to replace it every year or two, it would only be like $100 at wal mart.
LTL
White 2012 SV delivered 10 Dec 2011 returned 25 Nov 2014 replaced with stopgap ICE Sentra
[35 months] [35K miles] [9 Bars]
2013 Volt replaced after 36 months/30k miles with ICE Rogue
2016 SV-adjacent May 2016 lost 4th bar March 2018

User avatar
EVDRIVER
Moderator
Posts: 6677
Joined: Sat Apr 24, 2010 7:51 am

Re: How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 5:01 pm

LTLFTcomposite wrote:Something I've been wondering about the 12v battery though I haven't seen discussed... as an armchair EV engineer I'll submit this for your consideration...

"Hard driving" (acceleration, hill climbing, maybe lots of regen braking) shortens the life of the battery pack, right? i.e. the pack will last longer if you baby it, keeping the charging and discharging rates low? So how about "front ending" the big, expensive battery pack with a (much smaller) cheap lead acid battery that can absorb the "surges" and smooth out the current spikes to the main pack? So what if you have to replace it every year or two, it would only be like $100 at wal mart.

The regen is not that strong on the Leaf nor continuous for long periods of time, it's not going to shorten the life. That solution would not add life and would be costly, complicated, heavy, etc.

User avatar
EVDRIVER
Moderator
Posts: 6677
Joined: Sat Apr 24, 2010 7:51 am

Re: How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 5:03 pm

mwalsh wrote:What about the solar panel on the SL's spoiler? That should keep working as long as it's getting light, right?
\\Perfect to power an LED or tiny fan at best. It's absolutely insignificant.

danwat1234
Posts: 41
Joined: Sun Nov 14, 2010 9:19 pm

Re: How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 5:13 pm

EVDRIVER wrote:This has been discussed multiple times on many threads. The DC/DC charges the battery, not sure the charge current but it will be high likely. The DC/DC is off when key is off. What does the charge rate have to do with having something on? What type of constant load are you looking to have on all the time. if you give me details I can give you better info. The solar panel generates very little power and just trickle charges the 12V battery.
Well, say if the power is out and I need to plug in my 2 refrigerators, a few fluorescent lights and a few laptops to a 12VDC to 120AC inverter.. The car would be ideal to provide backup power. I guess we will just have to wait a bit until specs are released.

User avatar
mwalsh
Posts: 9644
Joined: Thu Apr 22, 2010 10:10 am
Delivery Date: 05 Jan 2011
Leaf Number: 0213
Location: Garden Grove, CA

Re: How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 6:54 pm

danwat1234 wrote:Well, say if the power is out and I need to plug in my 2 refrigerators, a few fluorescent lights and a few laptops to a 12VDC to 120AC inverter.. The car would be ideal to provide backup power. I guess we will just have to wait a bit until specs are released.
Uh, oh. I see someone voiding their battery warranty! :lol:
2011 Blue Ocean SL with 83,000 miles
2015 pack on 12/30/15
Tinted windows
Bosch AGM 12v
Ecopia 422+ tires
L1 EVSE upgrade
FIAMM horns
Superbright LED lighting
2013 sun visors
LED shifter
Heated seats
GT-R map lamp lenses
Altima illuminated door switches

User avatar
EVDRIVER
Moderator
Posts: 6677
Joined: Sat Apr 24, 2010 7:51 am

Re: How is the 12V battery recharged? Max amperage?

Tue Nov 16, 2010 7:25 pm

danwat1234 wrote:
EVDRIVER wrote:This has been discussed multiple times on many threads. The DC/DC charges the battery, not sure the charge current but it will be high likely. The DC/DC is off when key is off. What does the charge rate have to do with having something on? What type of constant load are you looking to have on all the time. if you give me details I can give you better info. The solar panel generates very little power and just trickle charges the 12V battery.
Well, say if the power is out and I need to plug in my 2 refrigerators, a few fluorescent lights and a few laptops to a 12VDC to 120AC inverter.. The car would be ideal to provide backup power. I guess we will just have to wait a bit until specs are released.

It is better to go straight to the pack.

Return to “Engineering”